1. Field of the Invention
The present invention relates to a closed type heat exchanger for an evaporation type cooling tower.
2. Description of Prior Art
There have been known and developed various closed type heat exchangers.
There is an increased demand for a closed type heat exchanger as disclosed in, for instance, Japanese Examined Utility Model Publication No. 3687/1978 in which bent portions 12 formed at both ends of a serpentine coil 11 are directly supported by a pair of frame members 10 to form a reed-screen-like coil unit 12 (FIG. 8 is referred to) and a requisite number of the coil units are used to put one upon another, thereby fabricating a desired closed type heat exchanger, from the viewpoint that assembling work is easy and allowability in design for determination of loads for cooling is large.
In the conventional heat exchanger fabricated by putting one reed-screen-like coil unit 13 on another in a multi-stage, the bent portions 12 at both sides of the serpentine coils 11 being supported by a pair of the frame members 10, there takes place Galvanic phenomenon due to electric potential difference between the frame members 10 and the bent portions which are made of different kind of metal from the frame members. This results in pin holes at the contacting areas between the frame members 10 and the bent portions 12, which cause leakage of cooling liquid. The corrosion in the coil units reduces the life time of the heat exchanger assembly.